In the fifth-generation wireless access system standard New Radio (NR), a unit in a frequency domain is a subcarrier and a unit in a time domain is an orthogonal frequency division multiplexing (OFDM) symbol. A resource element (RE) is a minimum physical resource, including one subcarrier in one OFDM symbol.
Specifically, a network device may configure one or a plurality of uplink/downlink bandwidth parts (BWP) for a terminal device. BWP is a subset of system carrier bandwidth, and the plurality of bandwidth parts may overlap in the frequency domain. A network device may activate one uplink/downlink bandwidth part in the configured bandwidth parts for the terminal device (for example, user equipment (UE)). The network device transmits a physical downlink shared channel (PDSCH) and a physical downlink control channel (PDCCH) to the terminal device in the activated downlink bandwidth part, and the terminal device transmits a physical uplink shared channel (PUSCH) to the network device in the activated uplink bandwidth part.
A plurality of BWPs configured by the network device for one or more terminal devices may overlap in the frequency domain, and a minimum granularity for configuring a BWP in the frequency domain is one resource block (RB), and each RB includes a plurality of subcarriers. Each RB in an overlapped location in a BWP of overlapped BWPs in the frequency domain can only be allocated to one terminal device at most. On such premise, how to efficiently allocate or re-allocate uplink or downlink resources by the network device to the terminal device becomes a technical problem that needs to be resolved.